Tag: Japan earthquake

The terribly destructive magnitude 9.0 earthquake which struck Japan on March 11, may have had another effect – Shortening the length of each Earth day and shifting its axis. Did you notice any change ?

Well according to NASA, the changes are so small that you won’t notice the difference.

Based on initial calculations conducted by Richard Gross, a research scientist at NASA’s Jet Propulsion Laboratory, the earthquake should have caused Earth to rotate just slightly faster, shortening the length of the day by about 1.8 microseconds (a microsecond is one millionth of a second), according to a statement released by NASA.

A reader posted this link to before and after photos

Gross used complex modeling and estimates of fault slippage to perform a preliminary theoretical calculation of how the earth’s rotation may have been affected.

Calculations by Gross also indicate that the position of Earth’s figure axis could have shifted by about 17 centimeters (6.5 inches), towards 133 degrees east longitude. The figure axis is the axis about which Earth’s mass is balanced.
Earth’s figure axis is therefore different and offset from the north-south axis by about 10 meters.

“This shift in Earth’s figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth’s axis in space-only external forces such as the gravitational attraction of the sun, moon and planets can do that,” according to the NASA statement.

The estimates for both the shortening in the Earth’s rotation and shift in the figure axis are preliminary and will very likely change as more data is collected and the calculations are refined.

The March 11 earthquake was the fifth largest since 1900. So far, over 4000 people are confirmed dead and the overall death total may exceed 10,000.

Several heavily damaged nuclear reactors at the Fukushima plant are in danger of meltdown as hero workers inside put their lives on the line to avoid a catastrophic failure and try to prevent the spread of lethal radiation.This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite

Previously, Gross had calculated the affects of the magnitude 8.8 Chilean quake in 2010 and found them to be slightly smaller compared to the Japanese quake. He calculated a shortening in the length of day of about 1.26 microseconds and shifting of Earth’s figure axis of about 8 centimeters (3 inches). These affects are dependent on the magnitude of the quake, exactly where it is located as well as how the particulars of how the fault slips.

In fact, Earth’s rotation is changing all the time as a result of continual changes in atmospheric winds and oceanic currents and these effects are about 550 times larger than the Japanese earthquake.

“Over the course of a year, the length of the day increases and decreases by about a millisecond,” says Gross. Indeed, the effects of earthquakes on changing rotation are so tiny that they are smaller than the margin of error in the measurements themselves.

By comparison, measurements of the figure axis are much more reliable and meaningful. Changes to the figure axis can be accurately measured to within about 5 centimeters. This means that the estimated 17 centimeter shift from the Japanese quake may be real after accounting for the effects of the atmospheric winds and ocean currents. Further research is needed as more data are collected and analyzed.

“These changes in Earth’s rotation are perfectly natural and happen all the time. People shouldn’t worry about them,” said Gross.